China is tightening its grip on Tibetan areas in the western part of the country by banning foreigners from the region ahead of the politically sensitive 50th anniversary of a failed Tibetan uprising.

Large swathes of Gansu, Sichuan and Qinghai provinces — home to large ethnic Tibetan communities — are now off limits to foreign travelers, local officials confirmed Thursday.

An official at the tourism office of northwestern Gansu province's Gannan Tibetan Autonomous Prefecture, home to a major monastery and large Tibetan communities, said the region was closed to foreigners and would not be open until late March. The official, who did not identify himself as is customary in China, did not say when the restrictions were put in place.

In Sichuan province, many areas open just two weeks ago are now closed to foreign tourists until April, according to officials at the Ganzi prefecture tourist bureau. Only three counties in that prefecture will remain open to foreigners. Qinghai province's tourism bureau also said that many areas remain closed to foreigners.

Foreign reporters are not allowed into Tibet without special permission. Entry to Tibetan-populated areas, however, had been permitted in the past. But after last year's riots, many areas were closed off and remain inaccessible.

Chinese officials did lead a rare and tightly controlled tour of Tibet this week for some foreign reporters. Several organizations, including The Associated Press, were excluded.